Thursday, September 14, 2017

Aliens have landed on my roof

Classes have begun at the college, a season about which I have selective amnesia.  No matter how many times I have done this (33 times, I'm counting), no matter how prepared I am with handouts and room arrangements is always nervewrackingly chaotic and utterly exhausting.  It's fun like riding a really big wave is, equal parts exhilaration and terror, and you can feel pretty bedraggled by the time you wash up on the beach.

And of course, while you are riding this wave of new school year energy, you can't do anything else. All this to say, it felt delightful today to have some quiet time to do some research and a bit of reading.

I had Jon Larsen's  In Search of Stardust1 on my stack of books to read because last spring the upper division research methods course I taught did an experiment to measure the heat capacities of meteorites, using the method developed by the Vatican Observatory's Guy Consolmagno, SJ and Bob Macke, SJ and colleagues.2 The students were curious about the astrochemistry context (where do the samples come from, how can you distinguish regular rocks from these stony aliens) and I've been collecting resources for this coming spring when a new batch of students will make these measurements.

I tend to think of meteorite strikes as spectacular and rare events, fireballs roaring through the sky that finally come crashing to earth.  Still they aren't as rare was you might think — tens of thousands of meteorites weighing as much or more than a euro coin hit the earth each year, most of them landing in the water.  But what takes my breath away are the hundreds of trillions of micrometeorites that come to rest on earth each year, adding as much as 100,000 metric tons to the earth's mass.  Invisible, unremarked.  Perhaps as many as one a day hits the roof of my house, there are surely some of these ancient bits of dust in the water I drink, still others stuck to my hands after weeding the garden.

Larsen, a Norwegian jazz musician, discovered that you could find and identify these micrometeorites by looking at the dust on urban roofs, previously it had been thought you couldn't find them in the midst of the general detritus of a city. But a careful eye is rewarded, as these cosmic intruders have a characteristic morphology. Their shape and appearance means you can sort them out under a microscope, much like Pasteur manually sorted the crystals of tartaric acid, and they are astonishingly beautiful.
From J. Larsen, In Search of Stardust , p. 51.

Larsen offers a brief and readable glimpse into the science of micrometeorites, but I enjoyed simply browsing the images, reading them as I might clouds.  There is a golden glass meteorite with deep blue inclusions (p 51) that looks like some alien aquatic creature's shell, while the burnished cryptocrystalline specimen on page 45 looks like a bronzed wasp's nest — until one remembers it is less than a millimeter long. One scanning electron microscopic image of an ablation spherule from the meteor that exploded over Chelyabinsk, Russia in 2013 looks like a tiny alien skull.

As much as I learned about the dust from outer space, Larsen's register of the terrestrial imposters gave me an entirely different view of road dust, which contains polished spheres of glass from the reflective markings on the roads and tiny crystals, microgemstones.

In one of the most beautiful passages in Isaiah (Is 54:11-12) we are told, "I lay your pavements in carnelians..." Who knew it was literally true.  The world is a beautiful place, if only we know where and how to look.

(A version of this post appeared at the Vatican Observatory Foundation's Catholic Astronomer blog.)

1. J. Larsen, In Search of Stardust   If you get it at Amazon through this link, the Vatican Observatory Foundation will get a donation. There was an article in the NY Times last spring about the project as well.

2. Guy J. Consolmagno, Martha W. Schaefer, Bradley E. Schaefer, Daniel T. Britt, Robert J. Macke, Michael C. Nolan, Ellen S. Howell, "The measurement of meteorite heat capacity at low temperatures using liquid nitrogen vaporization" Planetary and Space Science87 (2013) 146-156


  1. Thanks for summarizing such complex information into clear and interesting descriptions.
    I know the excitement and anxiety of starting a new semester. My starts were always accompanied with what I called my "first day of school nightmares." Not prepared, no materials, wrong day or time, room full of people, everyone shouting (including me), no one listening . . .! I rarely have the nightmare anymore, but I still question my preparedness for the first day -- even after all these years!
    Have a good year! Doris

    1. Have a wonderful year, too, Doris!